package com.seatiger.structure.map;

/**
 * 基于二分搜索树实现的map
 *
 * @param <K>
 * @param <V>
 */
public class BSTMap<K extends Comparable<K>, V> implements Map<K, V> {

    private class Node {
        private K key;
        private V value;
        private Node left;
        private Node right;

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
        }

        @Override
        public String toString() {
            return key.toString() + " : " + value.toString();
        }
    }

    private Node root;
    private int size;

    public BSTMap() {
        this.root = null;
        this.size = 0;
    }

    @Override
    public void add(K key, V value) {
        root = add(root, key, value);
    }

    /**
     * 向以node为根的二分搜索树中插入元素 （key,value）
     * 返回插入新节点后二分搜索树的根
     *
     * @param node
     * @param key
     * @param value
     * @return
     */
    public Node add(Node node, K key, V value) {
        if (node == null) {
            size++;
            return new Node(key, value);
        }
        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left, key, value);
        } else if (key.compareTo(node.key) > 0) {
            node.right = add(node.right, key, value);
        } else {
            node.value = value;
        }
        return node;
    }

    @Override
    public V remove(K key) {
        Node node = getNode(root, key);
        if (node == null) {
            return null;
        }
        root = remove(node,key);
        return node.value;
    }

    public Node remove(Node node,K key) {
        if (node == null) {
            return null;
        }
        if (key.compareTo(node.key) < 0){
            node.left = remove(node.left,key);
        }else if(key.compareTo(node.key) > 0) {
            node.right = remove(node.right,key);
        }else {
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }else if(node.right == null){
                Node leftNode = node.left;
                node.left = null;
                size--;
                return leftNode;
            }else {
                //找到后继节点
                Node successor = minimum(node.right);
                successor.right = removeMin(node.right);
                successor.left = node.left;
                node.left = node.right = null;
                return successor;
            }
        }

        return null;
    }

    @Override
    public boolean contains(K key) {
        return getNode(root,key) != null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(root,key);
        return node == null ? null : node.value;
    }

    @Override
    public void set(K key, V newValue) {
        Node node = getNode(root,key);
        if (node == null) {
            throw new IllegalArgumentException(key + "doesn't exist!");
        }
        node.value = newValue;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    private Node getNode(Node node, K key) {
        if (node == null) {
            return null;
        }
        if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else if (key.compareTo(node.key) > 0) {
            return getNode(node.right, key);
        } else {
            return node;
        }
    }

    /**
     * 返回以node为根的二分搜索树的最小值所在的节点
     * @param node
     * @return
     */
    private Node minimum(Node node){
        if(node.left == null) {
            return node;
        }
        return minimum(node.left);
    }

    /**
     * 删除以node为根的二分搜索树的最小节点
     * 返回删除后新二分搜索树的根
     * @param node
     * @return
     */
    private Node removeMin(Node node){
        if (node.left == null ){
            Node right = node.right;
            node.right = null;
            size--;
            return right;
        }
        node.left = removeMin(node.left);
        return node;
    }
}
